Security systems that detect intruders via one or more security cameras are generally known. Such systems may be based upon the use of a security guard that monitors the cameras for intruders and raises an alarm when he/she notices an intruder.
In other security systems, the detection of intruders is automatic. In such systems, the detection of intruders may be based upon the detection of motion within a field of view of a camera. In such systems, a computer is generally used to compare successive frames of video for changes between the successive frames. When a change of sufficient magnitude is detected and is recognized as an object of interest, e.g., a human, the computer alerts a security guard or central monitoring station.
In order to reduce costs, most security systems have only a single, central location that monitors for and that detects intruders. Where a secured area extends over a large geographic expanse (e.g., an airport), the bandwidth of bringing all video signals back to the monitoring location for the detection of motion is prohibitively large. In order to reduce bandwidth, video signals may be compressed for transmission using an appropriate compression algorithm (e.g., H.264).
However, processing the compressed video signal at the monitoring station is also problematic in terms of interpretation, e.g., detection of intruder. State-of-the-art intruder detection systems work in the uncompressed pixel domain. Therefore, the compressed video signal must be decompressed before the intruder detection algorithms may be applied. Decompression is a time consuming process; it often prevents real-time operation, such as motion detection used for intruder detection, unless multiple, expensive processors are used. Accordingly, a need exists for a better method of processing compressed video signals at the monitoring station.